Fig. 6. Black mats of Younger Dryas age (locality nos. refer to Fig. 1
and SI Table 2). Photographs are by the author unless indicated otherwise. (a)
The black mat at the Murray Springs Clovis site in Arizona (locality 1a) is a
black algal mat that blankets the Clovis occupation surface. (b) At the
Naco Clovis site (locality 1b) the mammoth bones and artifacts are directly
overlain by laminated marls and clay bands that are pond facies of the San Pedro
Valley black mat. (c) The type Clovis site in Blackwater Draw, New Mexico
(locality 5) has a dark-gray diatomite stratum D containing Folsom artifacts and
bones of Bison bison antiquus overlying a "brown sand wedge" (stratum C)
with Clovis artifacts and mammoth bones over a "gray sand" (stratum B) with
Clovis artifacts and bones of mammoth and B. bison antiquus beyond where
stratum C pinches out. Photograph courtesy of Glen L. Evans. (d) At the
Lubbock Lake site in Texas (locality 6) a black and white diatomite (stratum 2A)
(2d in SI-8) contains Folsom artifacts and bones of extinct bison and directly
overlies a gray fluvial sand (stratum 1B). Photograph courtesy of Vance T.
Holliday. (e) Folsom, Goshen-Plainview, and Agate Basin artifacts
are found in situ in the lower portions of the Leonard paleosol at
several sites in the Knife River - Lake Ilo region of North Dakota (locality 7).
Photograph by Stanley A. Ahler. Published courtesy of the Center for the Study
of the First Americans. (f) The Lindenmeier Folsom site in Colorado
(locality 8) has Folson artifacts and bison bones covered by a black cumulic
mollisol overlying Peoria loess.

Fig. 7. Black mats of Younger Dryas age (Locality numbers refer to
Fig. 1 and SI Table 2). Photographs are by the author unless indicated
otherwise. (a) The Goshen paleosol at the Hell Gap site (locality 9) is a
cumulic mollisol as seen here and an aquall in lower elevations. (b) At
the Agate Basin site (locality 10a) multiple black bands are separated by slope
wash alluvium. (c) Dennis Stanford (on left) and Adrian Hannus examine a
Clovis point in situ on an erosion surface covered by a cumuli mollisol
of YD age at the Lange-Ferguson site (locality 12). Note truncation of the
mollisol on the right. (d) The Domebo mammoth skeleton (locality 13) is
buried by dark gray organic clayey sand. Photograph courtesy of Frank C.
Leonhardy. (e)The Clovis occupation surface at the Aubrey site locality 14) is
overlain by a facies of the lacustrine organic clay and marl. Photograph
courtesy of C. Reid Ferring.(f) At the Feterman mammoth site (locality
15) a black cumulic mollisol of probable YD age overlies mammoth bones on older
terrace alluvium.

Fig. 8. Black mats of Younger Dryas age (locality numbers refer to
Fig. 1 and SI Table 2). Photographs are by the author unless indicated
otherwise. (a) At the Carter/Kerr-McGee site (locality 16) a black aquoll
overlies an erosional surface and contains Goshen and Folsom artifacts in its
basal portion. (b) The black cumulic mollisol at the Jim Pitts site
(locality 17a) contains Goshen, Folsom, and Agate Basin artifacts and overlies a
surface with preYD charcoal that is apparently not cultural. (c)
Dissection of Gilcrease Spring mound (locality 19b) revealed a black peat of YD
age. Figures in the background are excavating mammoth tusks in the stratum
directly under the peat. (d) Black peaty lens of "Black Mat 1" of YD age
on the Kaibito Plateau (locality 37) represents one of several localized wet
land relicts. (e) At the Wilson-Leonard site (locality 27) a dark gray
cienega soil of YD age underlies the Leanne paleosol shown here and overlies
what is believed to be a Clovis horizon. Photograph courtesy of Vance T.
Holliday. (f) At the Indian Creek site (locality 29) multiple black
organic stringers of YD age contain Folsom artifacts upstream and overlie a
Clovis horizon above Glacier Peak tephra downstream. Leslie Davis, the principal
investigator, provides scale at the Clovis locality.

Fig. 9. Black mats of Younger Dryas age (locality numbers refer to
Fig. 1 and SI Table 2). Photographs by the author unless indicated otherwise. (a)
The Arlington Springs site on Santa Rosa Island (locality 30) contains the
oldest human skeletal remains in North America. Human bones occur near the
bottom of a channel, to the right of the menu board, and below a lens containing
bones of an extinct large mouse (Peromyscus nesodytes). The overlying
black layers are of YD age. Photograph courtesy of G. James West. (b)
Clovis artifacts at the Arc site (locality 31a) near Lake Erie occur at the base
of the black peaty layer of YD age and on a late glacial diamicton. Photograph
by Kenneth Tankersley. Published courtesy of the Center for the Study of the
First Americans. (c) At the Frazier site (locality 23a) Agate Basin
artifacts occurred at the base of a black cumulic mollisol of YD age. The pick
rests on the top of the mollisol. (d) A Cody-complex bone bed at the
Jurgens site (locality 23b) occurred both on and in a black cumulic mollisol of
YD age. (e) At Lamb Spring (locality 38) YD strata included the channel
fill at lower left and the overlying dark gray strata. (f) A dark brown
to black mollisol of YD age at the Flaming Arrow site (locality 40a) is highly
bioturbated.